iPhone 6 Plus T-Mobile - Question

I am currently doing an Student exchange program in Israel , and my Mom is coming to visit me. And I have been trying to get a hold of the iPhone 6 Plus.
Yesterday my mom was at Willow Bend mall in Dallas, and she got a hold of the iPhone 6 Plus 128GB T-Mobile Version for a full price without a contract.
The guy at the Apple Store said it can be used with any Sim Card.
Now by reading online , I read it's Unlocked and some places say it's Locked..
Now I really need to know before she comes to Israel if it's really Unlocked.
I don't want $1,000 down the drain.

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